Kohlrabi
Brassica Oleracea Gongylodes
Kohlrabi, or German turnip, is a unique member of the Brassicaceae family known for its crunchy, bulbous stem. Originating from Europe, it is prized for its mild flavor and versatility in cooking. Gardeners appreciate its ease of growth and ability to thrive in various climates.
Everything it needs
9 essentials at a glance
Watering
Kohlrabi prefers consistent moisture but does not like to sit in water.
Water deeply once a week, allowing the top inch of soil to dry out between waterings. During hot weather, increase frequency to twice a week. Signs of over-watering include yellowing leaves and root rot, while under-watering can cause wilting and stunted growth.
Light
Kohlrabi thrives in full sun but can tolerate partial shade.
Ideally, it should receive at least 6 hours of direct sunlight daily. In hotter climates, some afternoon shade can help prevent bolting and sunburn.
Soil
This plant prefers well-draining, loamy soil with a pH range of 6.0 to 7.0.
A recommended potting mix includes compost, peat moss, and perlite to enhance drainage and nutrient retention.
Humidity
Kohlrabi enjoys moderate humidity levels, ideally between 40% to 60%.
To increase humidity, mist the leaves or place a humidifier nearby. Signs of low humidity include leaf curling and browning edges.
Temperature
Kohlrabi grows best in temperatures between 60°F and 75°F (15°C to 24°C).
It is hardy in zones 3-9, tolerating light frost but not extreme heat. In summer, provide shade to prevent bolting.
Fertilizing
Use a balanced fertilizer with an NPK ratio of 10-10-10 or similar.
Fertilize every 4-6 weeks during the growing season, starting when seedlings are 2-3 inches tall. Signs of nutrient deficiency include yellowing leaves and poor growth.
Pruning
Pruning is minimal for kohlrabi.
Remove any dead or yellowing leaves to promote airflow. If plants become overcrowded, thin them out to allow for better growth. Deadheading is not necessary.
Repotting
Kohlrabi is usually grown directly in the garden, but if grown in containers, repot when roots fill the pot or every 1-2 years.
Choose a pot 2 inches larger in diameter. Signs it needs repotting include roots growing out of the drainage holes.
Propagation
Kohlrabi is typically propagated from seeds.
Sow seeds 1/2 inch deep in well-prepared soil in early spring or late summer. Thin seedlings to 12 inches apart once they reach 2-3 inches tall for optimal growth.
When it's unhappy
Yellow leaves
Why it happens
This can be caused by nutrient deficiency or over-watering.
How to fix it
Check soil moisture levels and adjust watering. Fertilize with a balanced fertilizer if nutrient deficiency is suspected.
Bolting
Why it happens
Bolting occurs when kohlrabi experiences stress from high temperatures or inconsistent watering.
How to fix it
Provide consistent moisture and partial shade during hot weather to prevent stress.
Pests (e.g., aphids, cabbage worms)
Why it happens
Pests are attracted to kohlrabi, especially in warm weather.
How to fix it
Use insecticidal soap or neem oil to control infestations, and encourage beneficial insects like ladybugs.
Root rot
Why it happens
Over-watering or poorly draining soil can lead to root rot.
How to fix it
Ensure proper drainage and allow the soil to dry out between waterings.
Stunted growth
Why it happens
This can be due to poor soil quality or insufficient light.
How to fix it
Ensure the plant receives full sun and amend the soil with compost to improve fertility.
Care through the year
Spring
In spring, sow seeds directly in the garden or start indoors. Ensure soil is well-draining and keep the area weed-free.
Summer
During summer, provide consistent watering and partial shade if temperatures exceed 80°F (27°C) to prevent bolting.
Fall
In fall, harvest kohlrabi before the first hard frost. If left in the ground, mulch around the base to protect from light frost.
Winter
Kohlrabi is typically not grown in winter, but if you live in a mild climate, you can continue to harvest from late fall crops.
Toxicity & Safety
Kohlrabi is non-toxic to pets and children. All parts of the plant are safe for consumption, making it a great choice for family gardens.
Good to know
How often should I water my kohlrabi?
Water kohlrabi deeply once a week, allowing the top inch of soil to dry out between waterings. In hot weather, you may need to water twice a week.
Why are my kohlrabi leaves turning yellow?
Yellow leaves can indicate over-watering or nutrient deficiency. Check soil moisture and consider fertilizing if needed.
What is the best temperature for growing kohlrabi?
Kohlrabi thrives in temperatures between 60°F and 75°F (15°C to 24°C) and can tolerate light frost.
How do I prevent kohlrabi from bolting?
To prevent bolting, provide consistent moisture and consider providing partial shade during extremely hot weather.
Can kohlrabi be grown in containers?
Yes, kohlrabi can be successfully grown in containers. Ensure the pot is at least 12 inches deep and wide for adequate root space.
What pests should I watch for on kohlrabi?
Common pests include aphids and cabbage worms. Regularly inspect your plants and use insecticidal soap or neem oil if infestations occur.
When is the best time to harvest kohlrabi?
Kohlrabi is best harvested when the bulbs are 3-4 inches in diameter, typically 6-8 weeks after planting.
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